Equip your Doedicurus with a saddle, pick it up with an Argentavis and fly near rocks as it automatically harvests the stone as you fly. Level up the melee damage to harvest more stone with each swing. Level up your Argentavis’ weight capacity be an insane stone harvest team.
As a starter, you may think you won’t need a stone gatherer, such as the Doedicurus, since the Ankylo also mines stone, but, trust me, this fella will make your life a million times easier! Also, they are surprisingly good swimmers!